DO TELL: Nudging can also be used for dark purposes: The path of least resistance can easily direct people to do the wrong thing.

Policy wonks have nudged people to sign up for organ donation, to increase their pension contributions — and even insulate their homes by coupling home insulation with an attic-decluttering service. All we have to do is make it easy for people to do the right thing.

But what if you want people to do the wrong thing? The answer: make that easy; or make the right thing difficult. Messrs Thaler and Sunstein are well aware of the risk of malign nudges, and have been searching for the right word to describe them. Mr Thaler likes “sludge” — obfuscatory language or procedures that accidentally or deliberately encourage inertia. Voter ID laws, he says, are a good example of sludge, calculated to softly disenfranchise. Meanwhile Mr Sunstein has written an entire book about the “ethics of influence”.

And as we are starting to realise, Vladimir Putin is well aware of the opportunity that behavioural science presents, too. Rumours circulate that the Russian authorities are keen recruiters of young psychologists and behavioural economists; I have no proof of that, but it seems like a reasonable thing for the Russian government to do. I am willing to bet that not all of them are working on attic-decluttering.

You know who’s an expert at nudging? Satan. Just sayin’ . . . .